Stents are generally designed as tubular support structures that can be used in a variety of medical procedures to treat blockages, occlusions, narrowing ailments and other problems that restrict flow through body vessels. An expandable stent is radially compressed to a low-profile configuration for passage through a body vessel, and then, once in position at a treatment site, the stent may be radially expanded to a larger-diameter deployment configuration to contact and support the inner wall of the vessel. Such stents are generally classified as either balloon-expandable or self-expanding. Balloon-expandable stents expand in response to the inflation of a balloon, while self-expanding stents expand spontaneously when released from a delivery device.
Balloon-expandable stents may provide the benefits of high radial stiffness and strength, minimal recoil, and controlled behavior during expansion. Self-expanding stents may offer the advantages of low-profile delivery and elastic deployment. A self-expanding stent may be crimped by as much as a 3:1 ratio from an expanded to a low-profile configuration (e.g., from 10 mm to 7 Fr) and then substantially fully recover the expanded configuration when deployed. Many self-expanding stents are made of superelastic nickel-titanium alloys that can recover strains as high as 8-10%.
The inventors believe a stent that has the attributes of both balloon-expandable and self-expanding stents would be advantageous.